Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
From the I/O guide on Fan:ConstantVolume:
"This object models a constant air volume fan that is intended to operate continuously based on a time schedule. This fan will not cycle on and off based on cooling/heating load or other control signals (Ref: Fan:OnOff)."
The Fan:ConstantVolume has only two settings - on or off. You can't modulate flow.
The Fan:OnOff object can do this, but to do so "...this object must be used as part of a compound object that allows multiple fan speeds". That doesn't include an AirLoopHVAC.
The solution is to use a Fan:VariableVolume object, adjust the coefficients to match your fan, and then use the various schedules in the Controller:OutdoorAir object to force a specific air flow rate per your schedule.
